Most control of model railroading remote objects such as locomotives, rolling stock, etc. is done by sending remote control signals down the track or through the air. Both types of signal transmission can use analog or digital data. Examples of digital transmission include the National Model Railroad Association's standard Digital Command Control (DCC) that can be applied directly as a power signal on the track or radio transmitted through the air. There is currently very little control of the locomotive done through direct contact or through proximity detection.
Examples of direct contact control include volume adjustment of on-board sound systems, resetting microprocessors using a switch or jumper, selecting whether an on-board decoder is to be operated under DCC or Conventional Analog control, locking an engine into a direction state via Lionel's E-unit lockout, etc. There are a few examples of proximity control such as using a magnet to operate a latching switch in a model caboose, and magnets placed on model railroad track that trigger horn and/or bell sound effects when a locomotive passes over, but each of those controls operate one and only one effect as a simple on-off activation.